Toughening modification of diglycerol-based polylactide networks by incorporating poly(propylene sebacate) segments

Abstract

The reactions of a diglycerol-based 4-armed l-lactide oligomer (DG4LAO) with a degree of polymerization (n=10.5) per arm, a hydroxy-terminated propylene sebacate oligomer (H2PSeO, n=6.7) and methylenediphenyl 4,4′-diisocyanate (MDI) produced bio-based polyester-urethanes (PEU-LAO/PSeOs) with feed DG4LAO/H2PSeO weight ratios, 100/0, 75/25, 50/50, 25/75 and 0/100. The FT-IR analysis and chloroform extraction experiment revealed that polymer networks by urethane crosslinkages were certainly formed for all of the polymers except for PEU-LAO/PSeO 0/100 which is a liner polymer. Scanning electron microscopic analysis revealed that the oligolactate (LAO) and propylene sebacate oligomer (PSeO) segments are compatibilized for all of the copolymer networks. The differential scanning calorimetric analysis of PEU-LAO/PSeOs revealed that LAO segments did not crystallize but PSeO segments crystallized, and that melt crystallization efficiency of PSeO segments was much enhanced by the presence of LAO segments. The polarized optical microscope analysis revealed that PEU-LAO/PSeO 25/75 possessed the fastest melt-crystallization rate among all of the PEU-LAO/PSeOs. The elongation at break and tensile toughness for PEU-LAO/PSeOs 100/0–25/75 significantly increased with increasing PSeO fraction, even though those of PEU-LAO/PSeO 0/100 were very low.